1. Field of the Invention
The present invention relates to a system and a method for controlling engine idle speed based on operational state settings.
2. Background Art
Engine emissions requirements have become increasingly stringent with the passage of increasingly restrictive air quality legislation as time has progressed. As engine control strategies are adjusted to meet increasingly tighter emissions regulations, desired customer vehicle acceleration performance is becoming increasingly difficult to achieve.
One conventional approach at attempting to provide desired customer vehicle acceleration performance is to increase engine idle speed. The increased engine idle speed is typically used when a vehicle is traveling (i.e., not parked and with the transmission in gear).
Further, when the vehicle where the engine is implemented is a fire truck, a relatively low engine idle speed is generally desirable to provide power (i.e., rotational torque and speed) to a water pump that provides pressurized water to hoses when the vehicle is parked (e.g., the parking brake is engaged) and the engine is at an idle state (or mode of operation). The reduced idle speed typically causes reduced engagement torque to the water pump. The water pump is typically driven by an auxiliary shaft (e.g., a power take off, PTO, drive shaft from the vehicle transmission) when the PTO (and hence the water pump) is engaged. Yet further, when the vehicle where the engine is implemented is a utility or industrial service (e.g., electric service, cable television service, forestry service, etc.) truck, a relatively low engine idle speed is generally desirable to provide power via the PTO drive shaft to any of accessories such as a hydraulic pump that provides pressurized oil to hydraulic mechanisms, an electrical power generator, a mechanical winch, a mechanical saw, and the like when the vehicle is parked.
Thus, there exists a need and an opportunity for an improved system and an improved method for engine idle speed control.